Sensorless backup for motor speed and position

Abstract

A method and system are contemplated for determining a final speed and position of a motor used in an electric vehicle. The final speed and position is calculated as a function of a sensed position when a resolver of a position system is available and as a function of a sensorless position when the resolver is unavailable.

What is claimed is: 
     
         1 . A method for determining a final speed and position of a motor used in an electric vehicle, the method comprising:
 calculating the final speed and position as a function of a sensed position with a resolver when the resolver is available, the sensed position being generated by the resolver responsively to measuring rotation of the motor;   calculating the final speed and position of the motor as a function of a sensorless position by switching to a sensorless system from the resolver when the resolver is unavailable to provide the sensed position or the sensed position by the resolver is in need of supplementation; and   controlling the motor by implementing a shutdown of the motor when the resolver is unavailable and the senseless system is unavailable.   
     
     
         2 . The method according to  claim 1  further comprising, after calculating the final speed and position according to the sensed position, executing an initialization mode before calculating the final speed and position as a function of the sensorless position. 
     
     
         3 . The method according to  claim 1  further comprising a position system including a first observer for calculating the final speed and position as a function of an angle error and one or more variables used to adjust gain. 
     
     
         4 . The method according to  claim 1  further comprising generating the final speed and position for use with a controller included within the vehicle, the controller being configured to process the final speed and position to control one or more vehicle operations. 
     
     
         5 . The method of  claim 1  including:
 determining a sensed position of the motor with a resolver responsively to measuring rotation of the motor; and 
 calculating a sensorless position with a sensorless system responsively to a voltage and a current of the motor, wherein the sensorless system is configured to adjust the voltage and the current to account for a timing difference between the motor based on the sensed position and the voltage and current based on the sensorless position. 
 
     
     
         6 . The method according to  claim 2  further comprising initializing the sensorless system with one or more last known values of the sensed position as part of the initialization mode. 
     
     
         7 . The method according to  claim 3  further comprising, when the resolver is available, determining the angle error as a function of a final position feedback for the final position, a final speed feedback for the final speed, and the sensed position. 
     
     
         8 . The method of  claim 5 , including operating the motor with a position system according to a first mode and a second mode, wherein the first mode calculating the final speed and position as a function of the sensed position, the second mode calculating the final speed and position as a function of the sensorless position. 
     
     
         9 . The method according to  claim 6  further comprising beginning a diagnostics process prior to beginning the initialization mode, the diagnostics process determining whether the resolver is available or unavailable. 
     
     
         10 . The method according to  claim 7  further comprising the sensorless system including a second observer and a third observer, the second observer calculating a sensorless angle error, the third observer calculating the sensorless position as a function of the sensorless angle error. 
     
     
         11 . The method according to  claim 9  further comprising completing the initialization mode before completing the diagnostics process. 
     
     
         12 . The method according to  claim 11  further comprising resetting the sensorless system responsively to the diagnostics process indicating the resolver to be available. 
     
     
         13 . The method according to  claim 12  further comprising resetting the sensorless system by zeroing the last known values or one or more other values associated with the sensorless system. 
     
     
         14 . A system for determining a final speed and position of a motor used in an electric vehicle, the system comprising:
 a resolver configured to determine a sensed position responsively to measuring rotation of the motor;   a sensorless system configured to calculate a sensorless position responsively to a voltage and a current of the motor; and   a position system configured to operate according to a first mode and a second mode, the first mode calculating the final speed and position as a function of the sensed position, the second mode calculating the final speed and position as a function of the sensorless position, wherein the sensorless system is configured to adjust a measurement of a voltage and a current to the motor to account for a timing offset resulting from a delay obtaining the measurement of the voltage and the current with the sensorless position.   
     
     
         15 . The system according to  claim 14  further comprising an initialization system configured to facilitate an initialization of the sensorless system while the position system is operating according to the first mode, the initialization system providing the sensorless system with one or more last known values of the position system. 
     
     
         16 . The system according to  claim 14  wherein the position system is configured to operate according to the first mode when the sensed position is available from the resolver and according to the second mode when the sensed position is unavailable and a speed of a vehicle having the motor is above a threshold, the threshold being associated with generating back electromotive force (EMF) sufficient for generating measurable amounts of the voltage and current, the measurable amounts being needed for the sensorless system to calculate the sensorless position. 
     
     
         17 . A system for determining a final speed and position of a motor used in an electric vehicle, the system comprising:
 a first observer configured to operate according to execution of a plurality of first instructions stored on a corresponding non-transitory computer readable storage medium, the first instructions being sufficient to:
 calculate the final speed and position as a function of an angle error; and 
 calculate the angle error as a function of a final position feedback, a final speed feedback, and either one of a sensed position and a sensorless position; 
   a second observer configured to operate according to execution of a plurality of second instructions stored on a corresponding non-transitory computer readable storage medium, the second instructions being sufficient to calculate a sensorless angle error as a function of a sensorless speed feedback, a sensorless flux, a sensorless DQ current and a sensorless DQ voltage; and   a third observer configured to operate according to execution of a plurality of third instructions stored on a corresponding non-transitory computer readable storage medium, the third instructions being sufficient to calculate a sensorless speed and the sensorless position as a function of the sensorless angle error and a sensorless speed feedback.   
     
     
         18 . The system according to  claim 17  wherein the third instructions are sufficient to:
 operate according to an initialization mode, the initialization mode including the third observer utilizing:
 the final position feedback as the sensorless position; and 
 the final speed as the sensorless speed; and 
 
 operate according to a running mode, the running mode including the third observer calculating the sensorless speed and position independently of the final speed and position. 
 
     
     
         19 . The system according to  claim 17  wherein the second instructions are sufficient to implement an adjustment for a timing difference between the motor and voltage and current readings used to calculate the sensorless DQ voltage and current. 
     
     
         20 . The system according to  claim 18  wherein the second instructions are sufficient to:
 operate according to the initialization mode, the initialization mode including the second observer utilizing the final speed and position to calculate the sensorless flux, the sensorless DQ current, and the sensorless DQ voltage; and 
 operate according to the running mode, the running mode including the second observer calculating the sensorless angle error as a function of the sensorless speed feedback.